Method for fabricating a plurality of elastic probes in a row

ABSTRACT

A method of forming a plurality of elastic probes in a row is disclosed. Firstly, a substrate is provided, then, a shaping layer is formed on the substrate so as to offer two flat surfaces in parallel. A photoresist layer is formed on the substrate and on the shaping layer. Then, the photoresist layer is patterned to form a plurality of slots crossing an interface between the two flat surfaces where a plurality of elastic probes are formed in the slots. In one embodiment, the interface is an edge slope of the shaping layer so that each of the elastic probes has at least an elastic bending portion. During chip probing, the shifting direction of the elastic probes due to overdrives is perpendicular to the arranging direction of the bonding pads so that the elastic probes are suitable for probing chips with high-density and fine-pitch bonding pads.

FIELD OF THE INVENTION

The present invention relates to a method of fabricating a plurality ofelastic probes in a row, and more particularly, to a method offabricating a plurality of elastic probes in a row which can scrubthrough the oxide layer on the high-density, fine-pitch bonding pads ofa semiconductor chip under testing.

BACKGROUND OF THE INVENTION

In a conventional IC tester, a probe card with probes is installed inthe test head of a tester. A flexible portion have been speciallydesigned in the probes of a probe card which can scrub through the oxidelayer on the bonding pads of an IC chip under test to ensure goodelectrical contacts. Conventional methods of manufacturing the probesinclude metal casting, extraction, or pressing, however, a tailor-madetooling is required which is very expensive where the shapes of theprobes are very limited. Moreover, as the pitches of the bonding padsbecome smaller and the densities of the bonding pads become higher,probes manufactured by conventional methods cannot meet the fine-pitchand high-density requirement of the bonding pads.

As revealed in R.O.C. Taiwan Patent publication No. 517320, John et al.discloses a method of manufacturing a plurality of flexible probes in arow using vapor deposition. As shown in FIG. 1, a substrate 10 isprovided which has a flat surface 11 where a plurality of probes 20 areformed on the flat surface 11 by sputtering, plating, or chemical-vapordeposition. A connecting bar 21 is connected to the probes 20. Eachprobe 20 has a contact point 22 and a flexible portion 23 bent in thehorizontal direction along the flat surface 11 of the substrate 10. Theprobes 20 are assembled to a probe card.

As shown in FIG. 2, an IC 30 under test has a plurality of bonding pads31. During chip probing, the contact points 22 of the probes 20 willcontact the bonding pads 31 of the IC 30. While the contact points 22 ofthe probes 20 are probing the bonding pads 31, the flexible portion 23of the probes 22 due to the overdrives will allow the contact points 22to shift in the same horizontal direction 32 to penetrate the oxidelayer on the bonding pads 31. However, the penetrating shift direction32 is parallel to the arranging direction of the bonding pads 31 whichcause electrical shorts between the probes 22 and damages to the IC, theprobe card or even the tester.

SUMMARY OF THE INVENTION

The main purpose of the present invention is to provide a method forfabricating a plurality of elastic probes in a row where a shaping layeris formed on a flat surface of a substrate to offer another flat surfaceand a photoresist layer is formed on the shaping layer. The photoresistlayer is patterned to form a plurality of slots crossing the interfaceof the two flat surfaces which partially expose the substrate and theshaping layer for forming the plurality of elastic probes. Therefore,the elastic bending portions of the probes are not parallel to the flatsurfaces of the substrate nor the shaping layer where the probes areformed. During chip probing, when the contact points of the probescontact the bonding pads of the chip, the probes due to overdrives willbe bent. The penetrating shift direction of the contact points isapproximately perpendicular to the arranging direction of the bondingpads which is suitable for probing chips with fine-pitch andhigh-density bonding pads. Moreover, the probes will not short to eachother during chip probing and the probes can easily installed on theprobe head to shorten the lead time of manufacturing a probe card.

The second purpose of the present invention is to provide a method forfabricating a plurality of elastic probes in a row where the shapinglayer is disposed and patterned on the substrate where an edge slope ofthe shaping layer is formed as an interface between the two flatsurfaces of the substrate and the shaping layer. Accordingly, each ofthe probes has two end portions on the substrate and/or on the shapinglayer and at least a flexible portion therebetween, wherein the flexibleportion is formed on the edge slope not parallel to the two endportions. The contacting points and the connecting points of the probesare formed in the two end portions. The edge slope of the shaping layerwill determine the shapes of the flexible portions to save the expensivetooling cost of fabricating different shapes of probes.

The third purpose of the present invention is to provide a method forfabricating a plurality of elastic probes in a row where the shapinglayer has an edge slope as an interface between the flat surfaces of thesubstrate and the shaping layer. A photoresist layer is formed on theflat surfaces of the substrate and the shaping layer. The photoresistlayer is then patterned to form a plurality of slots crossing the edgeslope to partially expose the flat surfaces of the substrate and theshaping layer for forming a plurality of elastic probes in a row.Therefore, the elastic bending portions of the probes are not parallelto the flat surfaces of the substrate nor the shaping layer. During chipprobing, the penetrating shift direction of the contact points of theprobes due to overdrives are approximately perpendicular to thearranging direction of the bonding pads on the IC chip without causingshorts between the elastic probes which are capable of probing a chipwith fine-pitch and high-density bonding pads. Moreover, the probes areinstalled or replaced on a probe head row by row to shorten the leadtime of manufacturing a probe card.

The fourth purpose of the present invention is to provide a method forfabricating a plurality of elastic probes in a row where a substrate isprovided. A recess is formed in the substrate to have a bottom and aplurality of inner sides to form the elastic bending portions of theelastic probes. The elastic probes have contact portions, connectingportions formed on the flat surface of the substrate and middle portionsformed on the bottom. The elastic bending portions are formed on theinner sides of the recess. The shapes of the elastic bending portionsare determined by the recess to save the tooling cost for fabricatingdifferent shapes of probes.

The fifth purpose of the present invention is to provide a probe pinassembly having a plurality of elastic probes in a row where each of theelastic probes has a first end portion, at least an elastic bendingportion, and a second end portion. The first end portions and the secondend portions are connected by the corresponding elastic bendingportions. All of the first end portions and all of the second endportions are formed on two flat planes which are parallel or coplanar.Moreover, the elastic bending portions are not parallel to the two flatplanes. Therefore, when probing high-density and fine-pitch bonding padsof a chip, probes will swift without cause shorts between the probes.

According to the present invention, a method for fabricating a pluralityof elastic probes in a row is revealed where each of the elastic probeshas a first end portion, a second end portion, and at least an elasticbending portion connecting the first end portion and the second endportion. A substrate is provided, and a shaping layer is formed on afirst flat surface of the substrate to offer a second flat surface,where an interface is formed between the exposed first flat surface andthe second flat surface. Then, a photoresist layer is formed on theshaping layer and on the substrate. Then, the photoresist layer ispatterned to form a plurality of slots crossing the interface topartially expose the substrate and the shaping layer for forming theelastic probes. Finally, a probe metal layer is formed in the slots sothat the first end portions of the elastic probes are formed on thefirst flat surface of the substrate, the second end portions on thesecond flat surface of the shaping layer, and the elastic bendingportions are formed on the interface.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a three-dimensional view of a conventional probe pin assemblyhaving elastic probes fabricated on a substrate.

FIG. 2 shows the penetrating shift direction of the elastic probes whenprobing an untested IC chip.

FIG. 3A to 3G are the cross sectional views of a substrate duringfabrication processes of a probe pin assembly having elastic probesaccording to the first embodiment of the present invention.

FIG. 4 shows the probe pin assembly when connecting to a probe headaccording to the first embodiment of the present invention.

FIG. 5 is the cross sectional view of the probe pin assembly placed onthe probe head according to the first embodiment of the presentinvention.

FIG. 6 shows the penetrating shift direction of the elastic probes whenprobing an untested IC chip according to the first embodiment of thepresent invention.

FIG. 7A to 7G are the cross sectional views of a substrate duringfabrication processes of a probe pin assembly having elastic probesaccording to the second embodiment of the present invention.

FIG. 8A to 8G are the cross sectional views of a substrate duringfabrication processes of a probe pin assembly having elastic probesaccording to the third embodiment of the present invention.

DETAIL DESCRIPTION OF THE INVENTION

Please refer to the attached drawings, the present invention will bedescribed by means of embodiment(s) below.

In the first embodiment according to present invention, a method forfabricating a plurality of elastic probes in a row is disclosed as shownin FIG. 3A to 3G. Firstly, as shown in FIG. 3A, a substrate 110 isprovided, where the substrate 110 is a semiconductor substrate having afirst flat surface 111. As shown in FIG. 3B, a shaping layer 120 isformed on the first flat surface 111 of the substrate 110, where atleast a portion of the first flat surface 111 is still exposed. Thematerial of the shaping layer 120 may selected from photoresist or theother material easy to pattern. The shaping layer 120 has a second flatsurface 121 higher than and parallel to the first flat surface 111. Inthis embodiment, the shaping layer 120 further has an edge slope 122 asan interface between the first flat surface 111 and the second flatsurface 121. Therein, the included angle between the first flat surface111 of the substrate 110 and the edge slope 122 ranges from 20 to 80degrees and the thickness of the shaping layer 120 ranges from 2 to 100micrometers. As shown in FIG. 3C, preferably, a release layer 130 isformed on the first flat surface 111 of the substrate 110 and on thesecond flat surface 121 and the edge slope 122 of the shaping layer 120.In this embodiment, the release layer 130 contains titanium formed bymetal sputtering.

As shown in FIG. 3D, a photoresist layer 140 is formed on the releaselayer 130 above the first flat surface 111, the second flat surface 121and the edge slope 122. The thickness of the photoresist layer 140 maybe thicker than the shaping layer 120. As shown in FIG. 3E, thephotoresist layer 140 is patterned to form a plurality of slots 141 byphotolithography. The slots 141 are configured for forming the pluralityof elastic probes, wherein the slots 141 cross the edge slope 122 fromthe first flat surface 111 to the second flat surface 121.

As shown in FIG. 3F, a probe metal layer 150 is formed in the slot 141by electroplating or electroless-plating. Please refer to FIGS. 3G and4, the probe metal layer 150 includes a plurality of elastic probes 160.The thickness of the probe metal layer 150 can be increased to enhancethe mechanical strength of the probes. Preferably, the probe metal layer151 is a multi-layer structure by plating, which includes at least anelastic support layer, a conductive layer, and an anti-adhesive metallayer (not shown in the figures). For example, the elastic support layercan be made of nickel or nickel-cobalt, the conductivity metal is madeof gold and formed on the elastic support layer for high speed and highfrequency testing, the anti-adhesive metal layer is made of palladiumand formed on the conductivity metal.

As shown in FIG. 3G, the photoresist layer 140 is stripped and therelease layer 150 is also etched so that the elastic probes 160 canseparate from the substrate 110 and the shaping layer 120. Each of theelastic probes 160 has a first end portion 161, a second end portion162, and at least an elastic bending portion 163 connecting the firstend portion 161 and the second end portion 162.

As shown in FIGS. 3F, 3G, and 4, at least a portion of the probe metallayer 150 lying on the first flat surface 111 of the substrate 110includes the first end portions 161 of the elastic probes 160. At leasta portion of the probe metal layer 150 lying on the second flat surface121 of the shaping layer 120 includes the second end portions 162 of theelastic probes 160. At least a portion of the probe metal layer 150lying on the edge slope 122 includes the elastic bending portions 163 ofthe elastic probes 160. Accordingly, all of the first end portions 161and all of the second end portions 162 are formed on two differentplanes in parallel. In this embodiment, the first end portions 161 ofthe elastic probe 160 are used as connecting ends and the second endportions 162 of the elastic probe 160 are used as contacting ends.Preferably, the slots 141 are connected together such that the probemetal layer 150 further comprises a connecting bar 151 integrallyconnecting to the elastic probes 160 (as shown in FIG. 4). In thisembodiment, the connecting bar 151 is connected to the contacting ends(one ends of the second end portion 162).

As shown in FIGS. 4 and 5, a probe head 300 has a plurality of alignmentholes 310, a plurality of connecting holes 320, and a plurality of probepads 321. Both ends of the connecting bar 151 are inserted into thealignment holes 310 of the probe head 300. Thereby, the first endportions 161 of the elastic probes 160 are aligned with the probe pads321 in the connecting holes 320 of the probe head 300. Solder 330electrically connect the elastic probes 160 and the probe pads 321.Then, the connecting bar 151 is separated from the probe contacting ends(one ends of the second end portions 162) of the elastic probes 160 bymetal etching or by mechanical breaking for probing IC.

As shown in FIG. 6, during chip probing, an IC 30 under test has aplurality of bonding pads 31 (or testing pads). The second end portions162 of the elastic probes 160 have contacting ends to probe the bondingpads 31 of the IC 30. The penetrating shifting direction 33 of theelastic probes 160 due to overdrives will be approximately perpendicularto the arranging direction of the bonding pads 31 of the IC 30 (thearranging direction of the elastic probes 160) so that the bonding pads31 will be short together. It is suitable for probing IC chips withfine-pitch and high-density bonding pads.

In the second embodiment of the present inventions, another method forfabricating a plurality of elastic probes in a row is shown from FIG. 7Ato 7G. As shown in FIG. 7A, firstly, a substrate 210 is provided, whichhas a first flat surface 211. As shown in FIG. 7B, a shaping layer 220is formed on the first flat surface 211 of the substrate 210 where theshaping layer 220 has a second flat surface 221 and a recess 222 toexpose at least a portion of the first flat surface 211. In thisembodiment, the depth of the recess 222 ranges from 2 to 100micrometers. The photoresist layer 220 further has a plurality of edgeslopes 223 in the recess 222 between the exposed first flat surface 211and the second flat surface 221. Therein, the included angle between theedge slopes 223 and the covered first flat surface 211 of the substrate210 ranges from 20 to 80 degrees. As shown in FIG. 7C, preferably, arelease layer 230 is formed on the first flat surface 211 of thesubstrate 210, the second flat surface 221, and the edge slopes 223 ofthe shaping layer 220 by means of metal sputtering. In this embodiment,the release layer 230 contains titanium and also can be used as aplating seed layer.

As shown in FIG. 7D, a photoresist layer 240 is formed on the releaselayer 230 and located above the first flat surface 211, the second flatsurface 221, and the edge slopes 223. The thickness of the photoresistlayer 240 is thicker than the shaping layer 220. As shown in FIG. 7E,the photoresist layer 240 is patterned to form a plurality of slots 241by photolithography where the slots 241 cross the edge slopes 223.

As shown in FIG. 7F, a probe metal layer 250 is disposed in the slots241 to form a plurality of elastic probes 260 in a row where the probemetal layer 250 is chosen from a group of conductive metals such asnickel, cobalt, tungsten, gold, palladium, copper, iron, alloy 42 orcopper alloy. As shown in FIG. 7G, the photoresist layer 240 is strippedso that the plurality of elastic probes 260 can easily separate from thesubstrate 210 and the shaping layer 220. Each of the elastic probes 260has a first end portion 261, a second end portion 262, a plurality ofelastic bending portions 263, and a middle portion 264. Referring toFIGS. 7F and 7G, at least a portion of the probe metal layer 250 on thesecond flat surface 221 of the shaping layer 220 includes the first endportions 261 and the second end portions 262 of the elastic probes 260where each first end portion 261 has a connecting end and each secondend portion 262 has a contact end. At least a portion of the probe metallayer 250 on the edge slopes 223 includes the plurality of elasticbending portions 263 of the elastic probes 260. At least a portion ofthe probe metal layer 250 on the first flat surface 211 of the substrate210 includes the middle portions 264 of the elastic probes 260 formed inthe recess 222. By means of the elastic bending portion 263 and themiddle portion 264 of the elastic probes 260, the penetrating shiftdirections of the contact ends (one ends of the second end portions 262)are different from row-arranging direction of the elastic probes 260,almost perpendicular. The elastic probes 260 will not short togetherduring probing an untested IC chip.

In the third embodiment of the present invention, another method forfabricating a plurality of elastic probes in a row is shown from FIG. 8Ato 8G. As shown in FIG. 8A, firstly, a substrate 410 is provided whichhas a flat surface 411. As shown in FIG. 8B, a recess 412 is created toform in the flat surface 411 of the substrate 410 by etching. The recess412 has two edge slopes 413 and a bottom 414. In the present embodiment,the included angle between the edge slopes 413 and the bottom 414 rangesfrom 100 to 170 degrees and the depth of the recess 412 ranges from 2 to100 micrometers. As shown in FIG. 8C, a release layer 420 is formed onthe flat surface 411 and on the edge slopes 413 and the bottom 414 ofthe recess 412. In the present embodiment, the release layer 420contains metal titanium to form elastic probes in a row.

As shown in FIG. 8D, a photoresist layer 430 is formed on the releaselayer 420 by spin coating to locate above the flat surface 411 and inthe recess 412. As shown in FIG. 8E, the photoresist layer 430 ispatterned by photolithography to form a plurality of slots 431 where theslots 431 extend across the recess 412 of the substrate 410 for forminga plurality of elastic probes 450 in the slots 431.

As shown in FIGS. 8F and 8G, a probe metal layer 440 is formed in theslots 431 to form a plurality of elastic probes 450 in a row. As shownin FIG. 8G, the patterned photoresist layer 430 is stripped so that theelastic probes 450 can separate from the substrate 410. Each of theelastic probes 450 has a first end portion 451, a plurality of elasticbending portions 453, a middle portion 454, and a second end portion452.

As shown in FIGS. 8F and 8G, at least a portion of the probe metal layer440 lying on the flat surface 411 of the substrate 410 includes thefirst end portions 451 and the second end portions 452 of the elasticprobes 450. At least a portion of the probe metal layer 440 lying on thebottom 414 of the recess 412 includes the middle portions 454 of theelastic probes 450. Moreover, at least a portion of the probe metallayer 440 lying on the edge slopes 413 of the recess 412 includes theelastic bending portions 453 of the elastic probes 450. In thisembodiment, the first end portions 451 have a plurality of connectingends of the elastic probes 450 for bonding to a probe head and thesecond end portion 452 have a plurality of contact ends of the elasticprobes 450 for chip probing. Therefore, the penetrating shift directionsof the elastic probes 450 are parallel each other but different from therow-arranging direction of the elastic probes 450. When probing anuntested IC chip, the second end portions 452 of the elastic probes 450can probe the bonding pads of the IC chip and the shift direction due tooverdrives is approximately perpendicular to the arranging direction ofthe bonding pads so that the probes will not be short to each other andwill not damage the bonding pads.

The above description of embodiments of this invention is intended to beillustrative and not limiting. Other embodiments of this invention willbe obvious to those skilled in the art in view of the above disclosure.

1. A method for fabricating a plurality of elastic probes in a row,wherein each of the elastic probes has a first end portion, a second endportion, and at least an elastic bending portion connecting the firstend portion and the second end portion, the method comprising the stepsof: providing a substrate having a first flat surface; forming a shapinglayer on the first flat surface of the substrate, the shaping layerhaving a second flat surface and exposing at least a portion of thefirst flat surface; forming a photoresist layer on the exposed firstflat surface of the substrate and on the second flat surface of theshaping layer; patterning the photoresist layer to form a plurality ofslots therein for forming the plurality of elastic probes, the slotscrossing an interface between the first flat surface and the second flatsurface; and forming a probe metal layer in the slots of the photoresistlayer, wherein at least a part of the probe metal layer lying on thefirst flat surface of the substrate includes the first end portions ofthe elastic probes, at least a part of the probe metal layer lying onthe second flat surface of the shaping layer includes the second endportions of the elastic probes, at least a part of the probe metal layerlying on the interface includes the elastic bending portions of theelastic probes.
 2. The method of claim 1, wherein the interface is anedge slope of the shaping layer.
 3. The method of claim 2, wherein theincluded angle between the edge slope and the covered first flat surfaceranges from 20 to 80 degrees, and the thickness of the shaping layerranges from 2 to 100 micrometers.
 4. The method of claim 1, furthercomprising the step of forming a release layer on the exposed first flatsurface of the substrate and on the second flat surface of the shapinglayer prior to forming the photoresist layer.
 5. The method of claim 4,wherein the release layer is formed by metal sputtering.
 6. The methodof claim 1, wherein the thickness of the photoresist layer is thickerthan the shaping layer.
 7. The method of claim 1, further comprising thestep of stripping the photoresist layer.
 8. The method of claim 1,further comprising the step of separating the probe metal layer from thesubstrate and the shaping layer to form the plurality of elastic probes.9. The method of claim 1, wherein the slots are connected together suchthat the probe metal layer further comprises a connecting bar integrallyconnecting the plurality of elastic probes.
 10. The method of claim 9,further comprising the steps of: placing the elastic probes by means ofthe connecting bar to a probe head; and removing the connecting bar fromthe plurality of elastic probes.
 11. The method of claim 1, wherein theprobe metal layer includes at least an elastic support layer, aconductive layer, and an anti-adhesive metal layer.
 12. A method forfabricating a plurality of elastic probes in a row, wherein each of theelastic probes has a first end portion, a plurality of elastic bendingportions, a middle portion, and a second end portion, the methodcomprising the steps of: providing a substrate having a first flatsurface; forming a shaping layer on the first flat surface of thesubstrate, the shaping layer having a second flat surface and exposingat least a portion of the first flat surface; forming a photoresistlayer on the exposed first flat surface of the substrate and on thesecond flat surface of the shaping layer; patterning the photoresistlayer to form a plurality of slots therein for forming the plurality ofelastic probes, the slots crossing a plurality of interfaces between thefirst flat surface and the second flat surface; and forming a probemetal layer in the slots of the photoresist layer, wherein at least apart of the probe metal layer lying on the first flat surface of thesubstrate includes the middle portion of the elastic probes, at least apart of the probe metal layer lying on the second flat surface of theshaping layer includes the first end portions and the second endportions of the elastic probes, at least a part of the probe metal layerlying on the interfaces includes the elastic bending portions of theelastic probes.
 13. The method of claim 12, wherein the shaping layerhas an opening between the interfaces for accommodating the middleportions, the interfaces are a plurality of edge slopes of the shapinglayer.
 14. The method of claim 13, wherein the included angle betweenthe edge slopes and the covered first flat surface of the substrateranges from 20 to 80 degrees, and the thickness of the shaping layerranges from 2 to 100 micrometers.
 15. The method of claim 12, furthercomprising the step of forming a release layer on the exposed first flatsurface of the substrate and on the second flat surface of the shapinglayer prior to forming the photoresist layer.
 16. The method of claim15, further comprising the step of separating the probe metal layer fromthe substrate and the shaping layer to form the plurality of elasticprobes by means of stripping the photoresist layer and removing therelease layer.
 17. The method of claim 12, wherein the slots areconnected together such that the probe metal layer further comprises aconnecting bar connecting the plurality of the elastic probes.
 18. Amethod for fabricating a plurality of elastic probes in a row, whereineach of the elastic probes has a first end portion, a plurality ofelastic bending portions, a middle portion, and a second end portion,the method comprising the steps of: providing a substrate having a flatsurface; creating a recess in the flat surface of the substrate, therecess having a bottom and a plurality of inner sides; forming aphotoresist layer on the flat surface of the substrate and in therecess; patterning the photoresist layer to form a plurality of slotscrossing the recess; and forming a probe metal layer in the slots of thephotoresist layer, wherein at least a part of the probe metal layerlying on the flat surface of the substrate includes the first endportions and the second end portions of the elastic probes, at least apart of the probe metal layer lying on the bottom of the recess includesthe middle portions of the elastic probes, at least a part of the probemetal layer lying on the inner sides of the recess includes the elasticbending portions of the elastic probes.
 19. The method of claim 18,wherein the inner sides of the recess are slopes.
 20. The method ofclaim 19, wherein the included angle between the inner sides and thebottom surface of the recess ranges from 100 to 170 degrees, and thedepth of the recess ranges from 2 to 100 micrometers.
 21. The method ofclaim 18, further comprising the step of forming a release layer on theexposed flat surface of the substrate and on the inner sides and thebottom of the recess prior to forming the photoresist layer.
 22. Themethod of claim 18, wherein the slots are connected together such thatthe probe metal layer further comprises a connecting bar connecting theplurality of the elastic probes.
 23. A probe pin assembly comprising aplurality of elastic probes in a row, each of the elastic probes havinga first end portion, at least an elastic bending portion, and a secondend portion, wherein the elastic bending portions connect thecorresponding first end portions and the corresponding second endportions, the first end portions are formed on a first flat plane, thesecond end portions are formed on a second flat plane, the first flatplane and the second flat plane are parallel or coplanar, the elasticbending portions are not parallel to the first flat plane nor the secondflat plane.
 24. The probe pin assembly of claim 23, further comprising aconnecting bar connecting the elastic probes.
 25. The probe pin assemblyof claim 23, wherein each of the elastic probes includes at least anelastic support layer, a conductive layer, and an anti-adhesive metallayer.